Hemodialysis is widely used to sustain life in individuals who have lost kidney function. The membrane material most commonly used for this purpose is regenerated cellulose. Regenerated cellulose is not inert; it stimulates the coagulation and complement systems and may be a cause of both acute and chronic morbidity for the patient. Further, its physical properties limit methods of sterilization and its usefulness for multiple use. A substitute for regenerated cellulose is being sought by device manufacturers. Our objective is to develop alternatives to regenerated cellulose. We will formulate a variety of polymers which should possess superior biocompatibility to regenerated cellulose, which have physical properties suited to reuse and alternative methods of sterilization, and which can be fabricated into membranes by economically viable methods. We will test the membranes in vitro to compare their biocompatibility to regenerated cellulose, examining their thrombogenic potential, their propensity to activate complement, and their direct action, if any, on the cellular components of blood. We will ensure the materials are resistant to the chemicals used for dialyzer reuse and that they can be fabricated into membranes with mass transfer properties suitable for hemodialysis. In Phase II, the most promising materials will be fabricated into dialyzers and our results confirmed in vivo using an animal model. This will lead to the development and clinical trials of clinical dialyzers in Phase III of the program.